Effect of inoculation methods and plants development stage on the reaction of cocoa Seedlings to Crinipellis perniciosa

摘要

Crinipellis perniciosa, the causal agent of witches' broom disease of cocoa has been threatening the sustentability of the cacao culture in South of Bahia. This research aimed found the better interaction between two inoculation methods and two stages of plant development in order to discriminate resistance reaction of cacao genotypes to the disease. Progenies of CATONGO (susceptible), THEOBAHIA (tolerant) and TSH, EET and TSA (intermediates) were inoculated with a suspension of 7.5 X 10~4 basidiospores/ml in one of the following stages of development: at 15 days of germination - when the cotyledons were opened or at 30 days of germination - second foliar flushing. The two methods of inoculation were: drops of inoculum handly placed or spray of inoculum through the belt spray system. A randomized block design was used with 12 treatments, 4 replications and 56 seedlings per plot, totalizing 2,688 seedlings. Sixty days after inoculation the plants were evaluated for each one of the following variables: terminal, axilary and cotiledonary brooms; and swellings of stem, petiole, pulvinus and hypocotile. It was observed the need of using a standard susceptible genotype more uniform and reliable than an open pollinated progeny of CATONGO. Inoculationsof seedling at the cotiledonary stage of development using the belt spray system was the more efficient treatment to differentiate genotypes reactions to C. perniciosa.